An understanding of the waste water nature, from both the qualitative and quantitative points of view, is a fundamental factor in the selection of treatment techniques and their subsequent operation. This is even more so in the case of small communities whose discharges are more subject to variation. An analysis of French data in this field provides values for small communities in rural areas (the majority). So far as other communities are concerned there are three examples which particularly illustrate the effects of the different factors (way of life…) on specific loads.